Sorry, I've missed the isolated atom energy: -306.74916142 Ry Giovanni
> On 13 Oct 2015, at 15:39, Giovanni Cantele <[email protected]> > wrote: > > A quick run using your input (that demonstrates that providing inputs results > in quicker answers!!!) as is (so non lattice constant optimisation), > gives: > > bulk Zr : -614.4200082344 Ry > isolated atom: > > where the isolated atom was reproduced using the same input with just one > atom, a=12, c=15 (just more or less safe values for an isolated atom), > nspin=2, > starting_magnetization(1) = 0.5, KPOINTS { gamma }. The final magnetic moment > on the isolated Zr atom is 2.00. > > Cohesive energy: (-614.4200082344 - 2 * -306.74916142) / 2 * 13.605692 ~ > -6.27 eV per Zr atom > > So, the value matches what you reported from the USPP calculations. Are you > sure that in calculating with PAW the cohesive energy you are using, for the > isolated Zr atom, its PAW energy (so, did you remake the calculation for the > atom and use that energy for calculating the cohesive energy)? Energy coming > from > different pseudo potentials cannot be used within the same formula, because > they are referred to a different zero. > > Hope this helps, > > Giovanni > > > PS because you fix a quite strict criterion for the convergence of the scf > cycle (conv_thr=1.0D-9) I stopped the calculation for the isolated atom when > estimated scf accuracy < 5.5E-09 Ry > > >> On 13 Oct 2015, at 14:54, Vic Bermudez <[email protected]> wrote: >> >> Hello, >> >> I'm encountering some strange behavior in calculations for the lattice >> constants and cohesive energy of Zr metal. All calculations are being done >> using version 5.0. >> >> (1) I first find the energy of the free Zr atom, taking care to obtain the >> proper triplet ground state of the free atom. >> >> (2) I then optimize the (hexagonal) Zr metal lattice constants using a >> script that varies a0 over a range of values while doing vc_relax to >> optimize c0 at each value of a0. From this I find the values of a0 and c0 >> that give an absolute-minimum total energy >> >> When I do this using PBE with a USPP for Zr (Zr.pbe-nsp-van.UPF), which >> I >> obtained from the QE website, the results are very good. I find a0=3.235 >> Angstroms, c0=5.148 Angstroms and a cohesive energy of 6.23 eV/Zr, all of >> which are very close to the experimental values. So far, so good. >> >> When I repeat this procedure using PBE with a PAW pseudopotential >> (Zr.pbe-spn-kjpaw_psl.0.2.3.UPF), which I obtained from the THEOS website, I >> get essentially the same lattice constants, but the cohesive energy is >> wildly wrong (about 41 eV/Zr !!). I get the same results for >> ecutwfc=40/ecutrho=320 and ecutwfc=70/ecutrho=560. Except for the choice of >> PP, I'm using all the same input parameters for PAW as I did for USPP. Also, >> I get the same ridiculous cohesive energy whether I use the PAW total >> energies or the all-electron energies. Since the lattice constants are good, >> and, according to THEOS, the pseudopotential is well-tested, I must be doing >> something spectacularly wrong in obtaining or interpreting the energy >> values. >> >> Any advice would be much appreciated. In case it will help, I'm >> inserting a >> representative input file below (for relaxing with the optimized lattice >> constants). >> >> ****************** >> >> &CONTROL >> calculation='relax', >> restart_mode='from_scratch', >> title='single-crystal alpha-Zr - testing Zr PBE/PAW pseudopotential', >> pseudo_dir='/lustre/cmf/scratch/b/bermudez/QE_PP/', >> ! outdir='/lustre/cmf/scratch/b/bermudez/aZr/', >> etot_conv_thr=1.0D-5, >> forc_conv_thr=1.0D-4, >> nstep=10000, >> wf_collect=.TRUE., >> verbosity='default' >> / >> >> &SYSTEM >> ibrav=4, >> a=3.24, c=5.147, >> nat=2, >> ntyp=1, >> ecutwfc=40.0, >> ecutrho=320.0, >> occupations='smearing', >> smearing='gaussian', >> degauss=0.002 >> / >> >> &ELECTRONS >> electron_maxstep=200, >> conv_thr=1.0D-9, >> mixing_mode='plain', >> mixing_beta=0.7D0 >> / >> >> &IONS >> ion_dynamics='bfgs', >> upscale=10000.D0 >> / >> >> ATOMIC_SPECIES >> Zr 91.22 Zr.pbe-spn-kjpaw_psl.0.2.3.UPF >> >> ATOMIC_POSITIONS {crystal} >> Zr 0.000 0.000 0.000 >> Zr 0.333 0.667 0.500 >> >> K_POINTS {automatic} >> 10 10 6 0 0 0 >> >> ******************* >> >> Best Wishes, >> Vic Bermudez >> >> Victor M. Bermudez >> E-mail: [email protected] >> >> >> _______________________________________________ >> Pw_forum mailing list >> [email protected] >> http://pwscf.org/mailman/listinfo/pw_forum >> > > -- > > Giovanni Cantele, PhD > CNR-SPIN > c/o Dipartimento di Fisica > Universita' di Napoli "Federico II" > Complesso Universitario M. S. Angelo - Ed. 6 > Via Cintia, I-80126, Napoli, Italy > e-mail: [email protected] > Phone: +39 081 676910 > Skype contact: giocan74 > > ResearcherID: http://www.researcherid.com/rid/A-1951-2009 > Web page: http://people.na.infn.it/~cantele > > > > _______________________________________________ > Pw_forum mailing list > [email protected] > http://pwscf.org/mailman/listinfo/pw_forum > -- Giovanni Cantele, PhD CNR-SPIN c/o Dipartimento di Fisica Universita' di Napoli "Federico II" Complesso Universitario M. S. Angelo - Ed. 6 Via Cintia, I-80126, Napoli, Italy e-mail: [email protected] Phone: +39 081 676910 Skype contact: giocan74 ResearcherID: http://www.researcherid.com/rid/A-1951-2009 Web page: http://people.na.infn.it/~cantele _______________________________________________ Pw_forum mailing list [email protected] http://pwscf.org/mailman/listinfo/pw_forum
